Downhole bha seismic signal generator

ABSTRACT

A method for performing a seismic investigation during subterranean drilling operations includes connecting a bottom hole assembly to a drill string. The bottom hole assembly includes a drill bit and a vibration damper. The drill string is lowered into a borehole and rotated to drill the borehole to a greater length with the drill bit. An actual vibration generated by the bottom hole assembly is measured with a control system and the actual vibration is compared to a target seismic vibration range. When the actual vibration is outside of the target seismic vibration range, the dampening coefficient of the vibration damper is changed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Application No. 61/943,789, titled “Downhole BHA Seismic Signal Generator,” filed Feb. 24, 2014, the full disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to seismic surveying during drilling operations. More specifically, the disclosure relates to seismic signal generation by a bottom hole assembly during subterranean borehole formation.

2. Description of the Related Art

During drilling operations, it can be beneficial to have an understanding of the subterranean features. Down hole generated seismic waves could be used for many purposes such as studying formations above and below the well bore or for gathering necessary information to make steering decisions for the drilling assembly. Geo-steering is currently carried out by logging-while-drilling, which has very limited resolution and depth of penetration. In addition geo-steering cannot look ahead of the bit. Seismic-while-drilling has potentially much better penetration into the formation and has look-ahead capability to provide the driller with advance warning of drilling issues such as over-pressure in a vertical well, or deviation from the optimal distance from the bounding formations in a highly deviated well.

Prior methods of down hole generated seismic technology have relied on using the existing bit signature as the source waveform. This results in a chaotic source signature, giving the operator little or no control on source frequency range, power or wavelet shape. Such attempts in the past have involved intentionally designing a bit or a bottom hole assembly to vibrate during drilling. The problem with this method is that there is no way to control the frequency or amplitude of the resulting vibration. The vibrating system, comprising the bottom hole assembly, the drill string, and the rock formation are constantly changing with respect to each other. The formations are highly heterogeneous and variable, and normal drilling component wear and tear result in uncontrolled changes to the vibrational characteristics of the drilling assembly. These unplanned and uncontrolled changes can result in vibrational modes that do not work well for seismic investigation, that reduce drilling efficiency and rate of penetration, and that cause damage to hits, motors, measurement while drilling tools, logging-while-drilling tools, and other bottom hole assembly components.

SUMMARY OF THE DISCLOSURE

Embodiments of the apparatus and method of this disclosure are able to generate a frequency- and amplitude-controlled seismic signal at the drilling bottom hole assembly, or BHA, to be picked up by seismic or pressure sensors either downhole, behind the bit, in adjacent boreholes or at the surface. The controlled seismic signal can be generated by the bottom hole assembly by varying the natural frequency of the drilling assembly with a controlled variable dampening system. By using a controlled vibration, the source is better characterized and tuned for improved wavelet shaping, penetration and signal to noise compared to previous methods. An accelerometer or other vibration-measuring sensor could be included in the bottom hole assembly to record the source signature to aid in monitoring and adjusting the seismic source signal and to aid in signal processing and seismic imaging.

An active, programmable, variable stiffness vibration dampener is used to maintain the bottom hole assembly vibration in a desired frequency range and at an amplitude that will yield a usable seismic signal while minimizing the negative effects of this vibration on drilling performance and bottom hole assembly component life. This will avoid the problem of signal interference by shallow seismic reflectors that occur with surface seismic signal generation. This interference often makes seismic surveys in many parts of the world so poor that they are of little value. Embodiments of this disclosure could be used to study the deep formations above and below the borehole around and ahead of the drill bit or could be used to accurately determine where the formation boundaries are above and below the borehole in order to more accurately steer the drilling assembly.

According to an embodiment of the current disclosure, a method for performing a seismic investigation during subterranean drilling operations includes connecting the bottom hole assembly to a drill string. The bottom hole assembly includes a drill bit and a vibration damper. The drill string is lowered into a borehole and rotated to drill the borehole to a greater length with the drill bit. An actual vibration generated by the bottom hole assembly is measured with a control system that may include an accelerometer and the actual vibration is compared to a target seismic vibration range. When the actual vibration is outside of the target seismic vibration range, the dampening coefficient of the vibration damper is changed.

In certain embodiments, a return seismic signal returned from a subterranean feature from a source seismic signal generated by the bottom hole assembly is sensed with a plurality of sensors located along the drill string, attached to a casing, in an adjacent borehole, or at a surface, to image a formation around and ahead of the drill bit. The sensors can be multi-component seismic sensors or pressure sensors. The sensors can include at least three 3-component seismic sensors. After sensing the return seismic signal, the actual vibration can be compared to a target performance vibration and the dampening coefficient of the vibration damper can be changed when the actual vibration exceeds the target performance vibration. The steps of measuring the actual vibration, comparing the actual vibration to a target seismic vibration range, and changing the dampening coefficient of the vibration damper when the actual vibration is outside of the target seismic vibration range can be repeated until a target borehole length is reached with the drill bit. In certain other embodiments, the vibration damper comprises a damping piston having one or more adjustable orifices and changing the dampening coefficient of the vibration damper comprises generating a control signal using the control system and using the control signal to change the cross sectional area of the adjustable orifices. In yet other embodiments, the vibration damper includes a magneto rheological dampening fluid and the control signal is generated with the control system to change the viscosity of the magneto rheological dampening fluid. The control system can be part of the bottom hole assembly or be located outside of the borehole and can be used to change the dampening coefficient of the vibration damper.

In yet other embodiments, it can be the frequency of the actual vibration that is measured and compared to the target frequency range of seismic vibration. The dampening coefficient of the vibration damper can be changed when the frequency of the actual vibration is outside of the target frequency range of seismic vibration.

In other embodiments of the current disclosure, a method for performing the seismic investigation during subterranean drilling operations includes connecting the bottom hole assembly to the drill string. The bottom hole assembly includes the drill bit and the vibration damper. The drill string is lowered into the borehole and rotated to drill the borehole to a greater length with the drill bit. The actual vibration is measured by the bottom hole assembly with the control system. The target vibration range is selected from a group consisting of the target seismic vibration range and the target performance vibration range. The target seismic vibration range includes vibrations that generate the source seismic signal, and the target performance vibration range includes vibrations that improve the drilling performance. The actual vibration is compared to the target vibration range and if the actual vibration is outside of the target vibration range, the dampening coefficient of the vibration damper is changed.

In certain embodiments, the actual vibration is measured, the target vibration range is selected, the actual vibration is compared to the target vibration range and if the actual vibration is outside of the target vibration range, the dampening coefficient of the vibration damper is changed, until the target borehole length is reached with the drill bit. If the seismic vibration range is selected, the return seismic signal that has returned from the subterranean feature can be sensed with the plurality of sensors. In certain other embodiments, the vibration damper includes the magneto rheological dampening fluid and the control signal is generated with the control system to change the viscosity of the magneto rheological dampening fluid. The control system can be located outside of the borehole and be used to select the target vibration range.

In other alternative embodiments of the current application, an apparatus for performing the seismic investigation during subterranean drilling operations includes the bottom hole assembly connected to the drill string. The bottom hole assembly includes the drill bit and the vibration damper. The apparatus includes the control system for selectively measuring an actual vibration generated by the bottom hole assembly, comparing the actual vibration to the target vibration range, and changing the dampening coefficient of the vibration damper when the actual vibration is outside of the target vibration range.

In certain embodiments, the vibration damper has the magneto rheological dampening fluid and changing the viscosity of the magneto rheological dampening fluid changes the dampening coefficient of the vibration damper. In other embodiments, the vibration damper includes a piston and dampening fluid, wherein the piston includes at least one adjustable orifice. Varying the cross sectional area of at least one adjustable orifice is operable to change the dampening coefficient of the vibration damper. The apparatus can also include a communication means for transmitting the signals between the control system and the bottom hole assembly. The communication means can include mud pulse telemetry, acoustic telemetry, electro magnetic telemetry, or wired drill pipe.

In certain other embodiments, the apparatus can include the plurality of sensors for sensing the return seismic signal that has returned from the subterranean feature. The bottom hole assembly can have at least three 3-component seismic sensors. The control system can include a selector for switching the target vibration means between the target seismic vibration range and the target performance vibration range. The target seismic vibration range includes vibrations that generate the source seismic signal, and the target performance vibration range includes vibrations that improve the drilling performance. The apparatus can include a means of storing the information from the return seismic signals received by the sensors and for transmitting the return seismic signals to the surface for analysis. The apparatus may also have the means for processing and compression of data for transmittal to surface or later retrieval.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features, aspects and advantages of the disclosure, as well as others that will become apparent, are attained and can be understood in detail, a more particular description of the disclosure briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the drawings that form a part of this specification. It is to be noted, however, that the appended drawings illustrate only preferred embodiments of the disclosure and are, therefore, not to be considered limiting of the disclosure's scope, for the disclosure may admit to other equally effective embodiments.

FIG. 1 is a schematic representation of a portion of a subterranean well in accordance with an embodiment of the present disclosure.

FIG. 2 is a sectional view of a vibration damper of the production well of FIG. 1, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the disclosure. Embodiments of this disclosure may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout, and the prime notation, if used, indicates similar elements in alternative embodiments or positions.

In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present disclosure. However, it will be obvious to those skilled in the art that the present disclosure can be practiced without such specific details. Additionally, for the most part, details concerning well drilling, reservoir testing, well completion and the like have been omitted inasmuch as such details are not considered necessary to obtain a complete understanding of the present disclosure, and are considered to be within the skills of persons skilled in the relevant art.

Referring to FIG. 1, well system 11 includes borehole 13. In the illustrated embodiment, borehole 13 includes lateral bore 17 having heel 19 and toe 21 extending horizontally from borehole 13. Drill string 25 extends into borehole 13. Drill string 25 has bottom hole assembly 27 connected to its lower end. Bottom hole assembly 27 includes drill bit 29. When drill string 25 is lowered into borehole 13 and rotated, drill bit 29 drills borehole 13 to a greater length. Bottom hole assembly 27 can also include sub assembly 31. Sub assembly 31 can include a mechanical spring mechanism and motion guide. Due to high loads and limited space, sub assembly 31 can have a Bellville spring stack to act as a mechanical absorber. Alternately, a coil spring system could be used. Bottom hole assembly 27 can also include additional readily available shock, torsional bearing and other sub systems that absorb axial and torsional shocks and loads produced by the drilling process and help to maintain drill bit 29 in the bottom of the borehole to allow for continuous drilling, and can also include other subs and tools known in the industry that are used during drilling operations.

Bottom hole assembly 27 includes vibration damper 33. Vibration damper 33 is an active vibration damper. Active vibration dampers differ from passive vibration dampers in that in active vibration dampers, a feedback and control system is used to adjust the dampening coefficient based on changing operational conditions. A passive vibration damper does not have such a feedback and control system. Vibration damper 33 can use, for example magneto rheological dampening fluid with a variable viscosity, or can use variable valving to adjust the dampening coefficient. An example embodiment of vibration damper 33 is shown in FIG. 2.

Looking at FIG. 2, vibration damper 33 includes damper housing 35 that surrounds pipe segment 37 of drill string 25. Damper housing 35 can be a tubular member with an inner diameter that is larger than the outer diameter of pipe segment 37, so that an annular cavity 39 is defined between the inner diameter of damper housing 35 and the outer diameter of pipe segment 37. Vibration damper 33 has at least one double acting piston 38 with adjustable orifices 36 extending axially through double acting piston 38. Double acting piston 38 is attached to pipe segment 37 to define piston assembly 40 that includes both pipe segment 37 and double acting piston 38. Piston assembly 40 can move axially within damper housing 35. As piston assembly 40 moves axially within damper housing 35, fluids within annular cavity 39 pass through adjustable orifices 36 of double acting piston 38. Therefore, the ease at which piston assembly 40 is able to move within damper housing 35 is dependent both on the viscosity of the fluid within annular cavity 39 and on the number and size of adjustable orifices 36.

Magneto rheological fluid can be located within annular cavity 39. Magnetic coils 41 are located in double acting piston 38 in close proximity to adjustable orifices 36. If magneto rheological fluid is present, variations in the electrical current delivered to magnetic coils 41 will vary the dampening coefficient of vibration damper 33, which will change the damping of motion between damper housing 35 and piston assembly 40. For example, if the electrical current to magnetic coils 41 is increased, the magnetic field in annular cavity 39 of vibration damper 33 also increases. This causes the viscosity of the magneto rheological fluid to increase, making it more difficult for the fluid to pass through adjustable orifices 36, which in turn increases the dynamic stiffness of the vibration damper 33. Alternately, conventional fluids can be located within annular cavity 39 and the dampening coefficient of vibration damper 33 can be varied by adjusting the size of the cross sectional area of adjustable orifices 36 of double acting piston 38. For example, decreasing the cross sectional area of adjustable orifices 36 will make it more difficult for the fluid to pass through adjustable orifices 36, which in turn increases the dynamic stiffness of vibration damper 33, in other embodiments, both the viscosity of the magneto rheological fluid can be decreased and the cross sectional area of adjustable orifices 36 can be increased to decrease the dynamic stiffness of vibration damper 33. In each method, the opposite is also true in that decreasing the viscosity of the magneto rheological fluid or increasing the cross sectional area of adjustable orifices 36 will decrease the dynamic stiffness of vibration damper 33.

A control system 43 can be used to receive, process, and deliver information relating to the components of bottom hole assembly 27. Control system 43 can have electronics including axial, lateral, and torsional vibration sensors. Control system 43 can also have a pre-programmed microprocessor to receive the signals from sensors 47, calculate the optimum damping coefficient, and generate the control signal to send to magnetic coils 41 to vary the dampening coefficient. Returning to FIG. 1, control system 43 includes BHA control system 43 a that is part of bottom hole assembly 27. Control system 43 also includes a control system that is outside of borehole 13, such as surface control system 43 b. In alternative embodiments, only a BHA control system 43 a is used, or alternately, only surface control system 43 b is used. When surface control system 43 b is used, communication means 45 can be used to transfer signals between surface control system 43 b and bottom hole assembly 27. Communication means 45 within borehole 13 can be, for example, by way of mud pulse telemetry, acoustic telemetry, electro magnetic telemetry, or wired drill pipe. Alternately, wireless communication means 45 can also be used.

Control system 43 can be used to measure the actual vibrations of bottom hole assembly 27 during drilling operations. Control system 43 can also be used to process information relating to vibration measurements, such as comparing the measured actual vibrations to the target vibration range and generating the control signal to deliver to vibration damper 33 to vary the dampening coefficient of vibration damper 33. Control system 43 can measure, for example, the amplitude or frequency of the actual vibration and compare it to an amplitude or frequency of a target vibration range. Sub assembly 31, vibration damper 33, and control system 43 are shown in FIG. 1 as separate members. Having sub assembly 31, vibration damper 33, and control system 43 as separate members allows for more convenient maintenance operations. Alternately, sub assembly 31, vibration damper 33, and control system 43 can be integrated together in a single assembly to minimize tool size.

During seismic investigation operations the actual vibrations of bottom hole assembly 27 will be source seismic signal 42. During such seismic investigation operations, the target vibration range will be the target seismic vibration range. The target seismic vibration range will include vibrations of a desired or preferred amplitude or frequency for generating source seismic signal 42. Control system 43 can include the selector for switching the target vibration range between the target seismic vibration range and the target performance vibration range. During drilling operations but between seismic investigation operations, control system 43 can be used to switch the target vibration range to the target performance vibration range. The target performance vibration range will be a range of vibrations that improve the drilling performance. For example, the target performance vibration range can include a range of vibrations with an amplitude or frequency that maintains drill bit 29 in contact with the bottom of bore hole 13, increases the rate of penetration, and improves the life of drill bit 29.

Continuing to look at FIG. 1, bottom hole assembly 27 includes a number of sensors 47. In one embodiment, there are at least three sensors 47 and sensors 47 are 3-component seismic sensors. Sensors 47 are spaced at intervals along bottom hole assembly 27 closer to surface end 49 of drill string 25 than drill bit 29 or vibration damper 33. Sensors 47 can sense the returning seismic waves such as return seismic signal 51 that has returned from subterranean feature 53. Data sensed by sensors 47 can be transmitted to the operator by control system 43. In alternative embodiments, sensors 47 can be positioned at other locations within borehole 13, such as in the casing (not shown), or can be located outside of borehole 13 at surface 44 or in an adjacent borehole. The required frequency range can be determined by the desired depth of penetration of source seismic signal 42 and the spacing of sensors 47. The desired amplitude range can then be selected that will be high enough to provide sensors 47 with a clear signal but low enough to not cause damage to the bottom hole assembly components or to unduly degrade drilling efficiency. In alternate embodiments, sensors 47 can be pressure sensors.

Although the method and apparatus has been described for use in a lateral bore, in an alternative illustrated embodiment of FIG. 1, borehole 13′ has a vertical bore 17′. In such an embodiment, the use and functionality of drill string 25′, drill bit 29′, sub assembly 31′, vibration damper 33′, control system 43′, BHA control system 43 a′ and sensors 47′ correspond to the use and functionally similarly named elements of lateral bore 17, as described herein.

In an example of operation, with bottom hole assembly 27 connected to the bottom of drill string 25, drill string 25 is lowered in borehole 13. Drill string 25 is rotated and drill bit 29 drills borehole 13 to greater length or depth. During this drilling process, bottom hole assembly 27 will vibrate. Control system 43 measures these actual vibrations. The actual vibrations are compared to the target vibration range and if the actual vibration is outside of the target vibration range the dampening coefficient of vibration damper 33 is changed. If vibration damper 33 includes a magneto rheological dampening fluid control system 43 will change the viscosity of the magneto rheological dampening fluid in order to change the dampening coefficient of vibration damper 33. Alternately, the cross sectional area of adjustable orifices 36 can be adjusted to change the dampening coefficient of vibration damper 33.

As the drilling operations continue, the characteristics of the formation being drilled will change and bottom hole assembly 27 will wear. These variables, as well as others, will affect the vibration of bottom hole assembly 27. Therefore, control system 43 will continue to measure the actual vibrations either constantly or at preselected intervals, until the selected length of borehole 13 is reached, or the system is otherwise turned off.

During seismic investigation operations, the operator can use control system 43 to select the target seismic vibration range that generates a preferred source seismic signal. The vibrations of bottom hole assembly 27 will only be partially dampened to keep them out of the destructive range and to shift the natural vibration of bottom hole assembly 27 into the preferred range for source seismic signal 42. The actual vibrations of bottom hole assembly 27 will be source seismic signal 42. Such a controlled source will allow a reduction in source-generated noise during the sensing and processing of return seismic signal 51, as opposed to chaotic, nature of the source waveform if no vibration damper 33 was used or if a passive vibration damper was used. Maintaining the actual vibrations in the target seismic vibration range will also allow control of the source frequency range for better penetration of source seismic signal 42 into feature 53 of the formation. Source seismic signal 42 generated by bottom hole assembly 27 will propagate through surrounding subterranean feature 53. Return seismic signal 51 that has returned from subterranean feature 53 will be sensed by sensors 47. The information that is sensed by sensors 47 can be transmitted by control system 43 for recording and further processing to interpret the results and generate a seismic survey map to image the formation around and ahead of the drill bit 29.

Between seismic investigation operations, while rifling operations continue, the operator can instead use control system 43 to select the target performance vibration or target performance vibration range. The target performance vibration is a maximum vibration for optimizing drilling performance and the target performance vibration range is the range of vibrations that would result in improved drilling performance. For example, the target performance vibration range can include a range of amplitude and frequency of vibrations that maintains drill bit 29 in contact with the bottom of the bore hole 13, increases the rate of penetration, and improves the life of drill bit 29. This will allow the drilling operations to be performed more efficiently and effectively between seismic operations.

The present disclosure described herein, therefore, is well adapted to carry out the Objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the disclosure has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present disclosure and the scope of the appended claims. 

What is claimed is:
 1. A method for performing a seismic investigation during subterranean drilling operations, the method comprising: (a) connecting a bottom hole assembly to a drill string, the bottom hole assembly comprising a drill bit and a vibration damper; (b) lowering the drill string into a borehole and rotating the drill string to drill the borehole to a greater length with the drill bit; (c) measuring an actual vibration generated by the bottom hole assembly with a control system; (d) comparing the actual vibration to a target seismic vibration range; (e) changing the dampening coefficient of the vibration damper when the actual vibration is outside of the target seismic vibration range; and (f) repeating steps (c) through (e) until the actual vibration generated by the bottom hole assembly is within the target seismic vibration range.
 2. The method of claim 1, further comprising sensing a return seismic signal returned from a subterranean feature from a source seismic signal generated by the bottom hole assembly with a plurality of sensors to image a formation around and ahead of the drill bit, the plurality of sensors being located on one selected from a group consisting of along the drill string, attached to a casing, in an adjacent borehole, and at a surface.
 3. The method of claim 2, wherein the plurality of sensors are selected from a group consisting of multi-component seismic sensors and pressure sensors.
 4. The method of claim 2, wherein the plurality of sensors includes at least three 3-component seismic sensors.
 5. The method of claim 2, further comprising after sensing the return seismic signal, comparing the actual vibration to a target performance vibration and changing the dampening coefficient of the vibration damper when the actual vibration exceeds the target performance vibration.
 6. The method of claim 1, further comprising repeating steps (c) through (e) until a target borehole length is reached with the drill bit.
 7. The method of claim 1, wherein the vibration damper includes a magneto rheological dampening fluid and step (e) comprises generating a control signal with the control system to change the viscosity of the magneto rheological dampening fluid.
 8. The method of claim 1, wherein the vibration damper comprises a damping piston having one or more adjustable orifices and wherein changing the dampening coefficient of the vibration damper comprises generating a control signal using the control system and using the control signal to change the cross sectional area of the adjustable orifices.
 9. The method of claim 1, wherein the bottom hole assembly further comprises the control system and changing the dampening coefficient of the vibration damper comprises changing the dampening coefficient of the vibration damper with the control system.
 10. The method of claim 1, wherein the control system is located outside of the borehole and changing the dampening coefficient of the vibration damper comprises changing the dampening coefficient of the vibration damper with the control system.
 11. The method of claim 1, wherein: the step of measuring the actual vibration comprises measuring a frequency of the actual vibration; the step of comparing the actual vibration to the target seismic vibration range comprises comparing the frequency of the actual vibration to a target frequency range of seismic vibration; and the step of changing the dampening coefficient of the vibration damper when the actual vibration is outside of the target seismic vibration range, comprises changing the dampening coefficient of the vibration damper when the frequency of the actual vibration is outside of the target frequency range of seismic vibration.
 12. A method for performing a seismic investigation during subterranean drilling operations, the method comprising: (a) connecting a bottom hole assembly to a drill string, the bottom hole assembly comprising a drill bit and a vibration damper; (b) lowering the drill string into a borehole and rotating the drill string to drill the borehole to a greater length with the drill bit; (c) selecting a target vibration range from a group consisting of a target seismic vibration range and a target performance vibration range, the target seismic vibration range including vibrations that generate a source seismic signal and the target performance vibration range including vibrations that improve a drilling performance; (d) measuring an actual vibration generated by the bottom hole assembly with a control system; (e) comparing the actual vibration to the target vibration range; (f) changing the dampening coefficient of the vibration damper when the actual vibration is outside of the target vibration range; and (g) repeating steps (d) through (f) until the actual vibration generated by the bottom hole assembly is within the target seismic vibration range.
 13. The method of claim 12, further comprising repeating steps (d) through (f) until a target borehole length is reached with the drill bit.
 14. The method of claim 12, wherein step (c) comprises selecting the seismic vibration range, the method further comprising sensing a return seismic signal that has returned from a subterranean feature with a plurality of sensors.
 15. The method of claim 12, wherein the vibration damper includes a magneto rheological dampening fluid and step (f) comprises generating a control signal with the control system to change the viscosity of the magneto rheological dampening fluid.
 16. The method of claim 12, wherein the control system is located outside of the borehole and selecting a target vibration range comprises selecting a target vibration range with the control system.
 17. An apparatus for performing a seismic investigation during subterranean drilling operations, the apparatus comprising: a bottom hole assembly connected to a drill string, the bottom hole assembly comprising a drill bit and a vibration damper; and a control system operable for selectively measuring an actual vibration generated by the bottom hole assembly, comparing the actual vibration to a target vibration range, and changing the dampening coefficient of the vibration damper when the actual vibration is outside of the target vibration range until the actual vibration generated by the bottom hole assembly is within the target seismic vibration range.
 18. The apparatus of claim 17, wherein the vibration damper comprises a magneto rheological dampening fluid, wherein changing the viscosity of the magneto rheological dampening fluid changes the dampening coefficient of the vibration damper.
 19. The apparatus of claim 17, wherein the vibration damper comprises a piston and dampening fluid, wherein the piston includes at least one adjustable orifice, and varying the cross sectional area of the at least one adjustable orifice is operable to change the dampening coefficient of the vibration damper.
 20. The apparatus of claim 17, further comprising a communication means for transmitting signals between the control system and the bottom hole assembly, the communication means selected from a group consisting of mud pulse telemetry, acoustic telemetry, electro magnetic telemetry, or wired drill pipe.
 21. The apparatus of claim 17, further comprising a plurality of sensors for sensing a return seismic signal that has returned from a subterranean feature.
 22. The apparatus of claim 17, further comprising at least three 3-component seismic sensors for sensing a return seismic signal that has returned from a subterranean feature.
 23. The apparatus of claim 17, wherein the control system further comprises a selector for switching the target vibration means between a target seismic vibration range and a target performance vibration range, the target seismic vibration range including vibrations that generate a seismic signal and the target performance vibration range including vibrations that improve a drilling performance. 